import React, { Component } from 'react'

export default class Count extends Component {

    state = { count: 0 }

    increment = () => {
        // 获取当前的输入
        const { value } = this.selectNumber
        console.log(value)
        const { count } = this.state
        // value*1 是转换成 int 值 
        this.setState({ count: count + value * 1 })
    }
    decrement = () => {
        // 当前求和的值 
        const { count } = this.state
        // 当前选中的值 
        const { value } = this.selectNumber
        // 更新state
        this.setState({ count: count -value*1})
    }
    // 奇数加 
    incrementIfOdd = () => {
        const { count } = this.state
        const { value } = this.selectNumber
        if(count%2===1){
            this.setState({count:count+value*1})
        }
    }
    // 异步加 
    incrementAsync = () => {
        const { count } = this.state
        const { value } = this.selectNumber
        setTimeout(()=>{
            this.setState({ count: count +value*1})
        },300)
        
    }

    render() {
        return (
            <div>
                <h1>当前的求和为:{this.state.count}</h1>
                <select ref={c => this.selectNumber = c} >
                    <option value="1">1</option>
                    <option value="2">2</option>
                    <option value="3">3</option>
                </select>
                &nbsp;  &nbsp;
                <button onClick={this.increment}>+</button>
                &nbsp; &nbsp;
                <button onClick={this.decrement}>-</button>
                &nbsp;  &nbsp;
                <button onClick={this.incrementIfOdd}>当前求和为奇数在加</button>
                &nbsp;  &nbsp;
                <button onClick={this.incrementAsync}>异步加</button>
            </div>
        )
    }
}
